1. Field of Invention
This invention relates to grip materials for dampening vibrations and shocks transmitted through handles, and more particularly to a grip wrap material and method of applying the grip wrap material for dampening such shocks and vibrations.
2. Description of the Related Art
Heretofore a wide variety of shock and vibration dampening material and methods have been proposed and developed for dampening vibrations and shocks in handles. There are many human endeavors where a user or operator must firmly grip or hold an instrument or handle which is subject to transient mechanical vibration and shock. Such shocks may be individual, for instance when a tennis player strikes a tennis ball with a racquet, or repetitive. Repetitive shocks may further be classified as cyclic or acyclic. An example of a cyclic shock might be the shock felt by the operator of a pneumatic jackhammer. An acyclic shock may be exemplified by the shocks felt by a carpenter using a conventional hammer. While the succeeding discussion of shock-absorbing grips is focused on the sport of tennis, those having ordinary skill in the art will appreciate that the features and advantages of the present invention disclosed herein are applicable to a wide variety of gripping problems, such as baseball bats, golf clubs, hockey sticks, bicycle handlebars, and the like. Accordingly, the invention disclosed herein should be construed to include all forms of human endeavor wherein it is desirable to maintain a positive grip between an operator and handle while minimizing the impact force felt by the user through the handle.
Tennis is a well known sport which has been shown to subject players thereof to a wide variety of shock-related traumas. These include, but are not limited to: tennis elbow, more accurately elbow crunch; shoulder crunch; and wrist crunch. Each of these traumas is initiated and exacerbated by the shock or impact force caused by the impact of the tennis ball on the tennis racquet.
Elbow crunch is the excess centripetal force acting at the elbow, an excess that occurs because on impact the racquet slows down, so its centrifugal force drops. The centripetal force of the muscles attaching to the elbow and the centrifugal force of the racquet in its swing may balanced before the impact, but sudden slowdown creates what is effectively a muscle spasm. The muscle continues to contract as if it still had a full load, so it suddenly shortens and yanks on the tendons that attach to the elbow. Elbow crunch is a cyclic stress which, repeated over time, may be a contributing cause to tissue failure.
Shoulder crunch is the change in the centrifugal force acting on the racquet, a change that occurs due to impact slowing the racquet down, thus creating a sudden excess in centripetal force at the shoulder. Before, the centripetal force and centrifugal force were in equilibrium, but suddenly there is an excess centripetal force. This is effectively a muscle spasm in the shoulder muscles.
Wrist crunch is derived in the same manner as elbow crunch, only the distance is measured from the mass center to the wrist, not the elbow. This distance is equal to the distance from the wrist to the racquet's axis of rotation plus the distance from the axis of rotation to the balance point.
Impact force is the change in the racquet's momentum on impact, divided by the time it occurs. It is the force, or shock measured in Newtons, appearing at the mass center or balance point upon impact with the ball. For low resultant stresses on the arm, this impact should be low.
In order to minimize impact force, much effort has been expended by manufactures of tennis racquets and accessories. Tennis grips tend to present the designer thereof with several challenges. First, the grip must be sufficiently firm in the players hand such that he or she may deliver an accurate shot across the net to his or her opponent. The grip must, of necessity, take at least two forms. A first grip commonly utilized by tennis players is the so-called “Eastern” grip utilized by forehand shots. A second grip commonly utilized by tennis players is the so called “western” grip utilized for backhand shots. Of course, other grips may be used as well. It will be appreciated that during the course of the game, the player must rapidly and accurately shift from one grip to another, without reference to visually checking his or her grip. This necessitates a second desirable feature of tennis grips wraps; while they must provide a firm and accurate gripping surface for the player, they must also be capable of rapid and accurate realignment to an alternate grip. This characteristic is sometimes referred to as a grip wrap's “spinnability”.
A tennis player often generates considerable perspiration during the course of a match. Perspiration on the player's hands has generally been detrimental to maintaining a good grip with the racquet. This fact gives rise to a third desirable feature of tennis grips, which prior to the making of the present invention had yet to be adequately fulfilled; namely that the grip should minimize or be unaffected by the presence of perspiration on a player's hands during play.
To accomplish such features, manufactures have typically produced grip wrap materials which are applied, for instance by helically winding, about the bare handle of a tennis racquet. With reference to FIG. 1, these grip wraps, 101, typically take the form of an elongate composite formed of thin layer of a soft material 103, for instance felt, which is applied to one side of a waterproof tape 105, in this example a vinyl tape. This vinyl tape 105, with its underlying felt cushioning 103, is wrapped helically about the handle of the tennis racquet, not shown. Variations of this basic technology include defining one or more perforations, 107, along and through the length of vinyl tape 105, whereby the underlying felt cushioning is further used to absorb perspiration from the user's hands. One example of this technology may be found in U.S. Pat. No. 5,397,123 to Huang. Another variation includes mechanically texturing the surface of the vinyl tape or including the length of cord, 109, between the felt 103 and the vinyl 105, either of which is designed to improve the user's grip.
There are several problems with this methodology. A first, and most important problem is that the shock absorption or dampening of these grips is limited. During the development of the present invention a number of shock absorption tests were undertaken on both a grip constructed according to the principles hereinafter enumerated, and a number of existing tennis grip wraps which purport to be “shock-absorbing”. Graphs of three of these current tennis grip graphs are shown as prior art FIGS. 2–4. The test methodology employed for each grip is identical. A weight was dropped a distance of 1.5 inches onto a sample grip wrap and the resultant acceleration was plotted over time.
In the first test, shown in FIG. 2, a currently available commercial grip wrap hereinafter identified as “Y” was examined. The results of this test showed that for the standard weight, the perceived impact force measured as acceleration is 96.17 G, which impact force occurred over the time span of 1.80 milliseconds.
In the second test, shown in FIG. 3, a second currently available commercial grip hereinafter identified as “D” was examined. The results of this test showed that for the standard weight, the perceived impact force measured as acceleration is 113.44 G, which impact force occurred over a time span of 1.62 milliseconds.
In the third test, shown in FIG. 4, a third currently available commercial grip wrap hereinafter identified as “Y” was examined. The results of this test showed that for the standard weight, the perceived impact force measured as acceleration is 130.02 G, which impact force occurred over the time span of 1.20 milliseconds.
In order to improve on this shock absorption, two things must occur in order to minimize perceived impact shock. The overall acceleration must be lowered, and concomitantly the duration of the perceived impact shock should be increased.
What is needed therefor is device and method which will substantially decrease the perceived impact force felt by the user gripping a handle which is subject to impact forces. In order to accomplish this desirable result, the peak acceleration perceived by the user should be decrease. In order to effect this decrease, it is generally beneficial to increase the duration of the perceived impact force.
The invention provides such a grip, as well as one which is a secure grip despite widely varying conditions of ambient humidity, for instance the moisture or humidity formed by perspiration.
The present invention also provides such aforementioned secure grip, which enables the user to quickly shift grip without excessive “tackiness” of the grip, which would impair the spinnability thereof.